Membranes for biogas upgrading

Raw biogas contains anywhere from 55 to 65% methane, 30 to 45% carbon dioxide, and other trace gases such as hydrogen sulfide. These contaminants must be separated from the methane. One biogas upgrading technology is mem­brane- based gas permeation, where the different permeabilities of gases through membranes are utilized.
The advantages are: 

• reduced operational costs
• low investment
• easy to operate
• lower plant footprint and
• shorter installation times when using skid-mounted units
• flexible, modular
• no chemicals or others auxiliaries required
• no subsequent additional drying step

Evonik’s membrane modules make it possible to enrich methane to concentrates higher than 97% using only one compression step. Because of the high selectivity of the membrane and the unique membrane process design, the waste gas contains more than 99% CO2 and less than 0.5% methane, and thus does not need to be repurified.

Evonik is currently commissioning a pilot plant for upgrading biogas and, in cooperation with RWTH Aachen, is improving the process for the biogas up­grading itself. The performance of our process and products will be demonstrated in a real biogas production environment.